1. Field of the Invention
This invention relates to a system and method of providing a warning of a child in a vehicle childseat when conditions in the vehicle are unsafe. This application uses the term childseat to refer to any seating provided in a vehicle to accommodate a child.
2. Description of Related Art
Children's bodies have greater surface area to body mass ratio than adults, so they absorb more heat on a hot day. Children also have lower perspiration capacity than adults, so they are less able to dissipate body heat. The result is tragic losses of children's lives have occurred due to the child being restrained in a vehicle childseat when the vehicle is parked and overheats inside. The American Academy of Pediatrics warns on their website (http://www.aap.org/family/carseatguide.htm) not to leave a child unattended in a car safety seat as temperatures can reach deadly levels in minutes, and the child can die of heat stroke.
Alarm systems to protect children from this unsafe condition are known in the art. U.S. Pat. No. 5,793,291 (Thornton) provides a system using a motion detector and a temperature detecting element coupled to a NOR gate. The system uses the motion detector to determine if person is in an automobile, and the temperature detector to determine if an extreme temperature also exists. If both conditions exist, it sounds the automobile horn. A possible problem with this system is children may be sleeping and making little or no motion while still at risk. U.S. Pat. No. 5,949,340 (Rossi) describes a system with an automobile infant seat occupancy sensor of the switch, optical detector, heat detector, or weight detector type, that provides a reminder signal to fasten the safety harness on the seat. When the ignition of the automobile is turned off, the system provides an alarm to remind that the seat is still occupied. A more urgent warning may be provided if the child is not removed within a predetermined time period. Also described is an embodiment that incorporates a vehicle interior temperature sensor. This embodiment may perform various operations to alleviate harm coming of the seat occupant such as starting the vehicle air conditioning, opening the windows, or transmit a message to a remote location. U.S. Pat. No. 6,028,509 (Rice) describes a system that uses a temperature measuring circuit which provides an output signal when a particular high temperature is sensed, and a sound sensor which is adjusted to detect the high pitched sounds emitted by a child. The signals for these sensing devices are received by an AND gate and when both the high temperature is detected and the sounds of a child the system provides an alarm. A possible problem with this system is children may be sleeping and making little or no sound while still at risk. U.S. Pat. No. 6,819,249 (Papp) describes a system employing a plurality of pressure sensors incorporated into the seats of a vehicle. These sensors send a signal to the system processor to indicate the seat is occupied. The system alarms when the seats are occupied when the vehicle ignition is turned off, or, alternately the transmission placed in the park position. An embodiment of the system employs motion detectors. A NASA News Release describes a child car-seat safety device which senses when a child occupies a particular seat and a portable driver alarm is carried by the driver on a key ring. The alarm sounds when the child is in the seat and the portable driver alarm is a set distance from the sensor for a set period of time.
The systems described above present complexities in installation, operation, and in the cases of U.S. Pat. Nos. 5,949,340 (Rossi) and 6,819,249 (Papp), a high frequency of apparently unnecessary alarms. The NASA developed system also has high potential for unwanted alarms and does not address a situation where both parents may use the system. These are all undesirable features that tend to discourage use of these systems. The systems complexity makes their valuable child protection potential expensive, tending to discourage their use. There exists a need for an alarm system to protect children that is inexpensive, simple to use and install, and which alarms only when a serious threat appears.